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Storing Dry Foods

STORAGE LIFE OF DRY FOODS
In Consultation with Stephen Portela

Determining the storage life of foods is at best an inexact science as there are so many variables. These range from the condition your food was in when you first purchased it and many other factors. This page was written with input by Mr. Stephen Portela who has over 30 years of professional food storage experience. This information should be used as a general guide only, and should not be followed "as the gospel truth" because your results may be different.

FOUR FACTORS THAT AFFECT FOOD STORAGE

Factor #1: The TemperatureTemperature has more to do with how long well dried foods store than anything else. The USDA states, "Each 5.6oC. (10.08oF) drop in temperature doubles the storage life of the seeds". Obviously, there is a limit as to how far this statement can be taken. However I expect it basically holds true from room temperature down to freezing. No doubt, the inverse could also be considered true. "Each 5.6oC. (10.08oF) rise in temperature halves the storage life of seeds." This theory holds true for non-garden seeds as well.

Storage Life Depending on CONSTANT Temperature

Note: this chart is not for a specific food but shows the relationship between temperature and storage life. Let's look at a couple of real life examples of good and poor food storage practices:

About a year ago we got an unopened paper bag of white flour which had been stored at 70oF, in a dry climate. It had been sitting for 3 years in a closet. It made fine looking bread but had such an 'old' and bad flavor that it was difficult to eat.

For another example, a couple of years ago in the Puget Sound area we were given a 4 gallon can of wheat that had been stored up high in a garage for about 30 years. This part of the country is not as hot as some places, yet in the summers the average garage still gets up into the 90's. Even though wheat will store for 30+ years under good conditions, the bread from this particular wheat was very bad tasting and after a few batches we ended up throwing the wheat away (something I always dislike doing).

oF

oC

Storage Life
in Years

37.6

3.1

40

48.4

9.1

30

59.2

15.1

20

70.0

21.1

10

80.8

27.1

5

91.6

33.1

2.5

102.4

39.1

1.25

Counter these stories with several examples told by Mr. Stephen Portela, Walton Feed's manager: He stores his long term food storage in his basement where the temperature hovers around 60oF. The experts give brown rice a 6 month storage life because of all the oils in it that go rancid. Yet, Mr. Portela has been eating from a supply of brown rice that has been in his basement over 10 years. It is still wholesome! In another example, there is a family living near him who purchased a supply of food in #10 cans 30 years ago. Their basement hovers around 58oF. After 28 years, Mr. Portela took a sample of many of these items to the Benson Institute at BYU to have it tested. The results can be seen at the bottom of http://waltonfeed.com/portela.html Mr. Portela's welcome page. You will see everything tested had a 'good' to 'satisfactory' rating except for the eggs which had a 'minimum passing' rating. After 28 years I think it is most interesting that it passed at all. Mr. Portela tells me as 30 years have now passed, their storage is still in very good condition. The bottom line is even with the very best packaging methods, if you are planning on storing your food in a warm environment, it will only last a fraction of the time it would last if stored in a cool, dry place. It is important you also find a place where the temperature remains constant. Frequent temperature changes shorten storage life. If you don't have a cool place for your food storage, plan on rotating your storage quickly enough to prevent food loss.Factor #2: Product Moisture ContentBy looking at the USDA nutritional tables, dry beans, grains, and flours contain an average of 10% moisture. Although it is very difficult and unnecessary to remove all moisture from dry foods, it is imperative that any food be stored as dry as possible. Foods with excess moisture can spoil right in their containers. This is an important consideration when packing food with dry ice as moisture condenses and freezes on the outer surface of the dry ice. For long term storage, grains should have a moisture content of 10% or less. It is difficult to accurately measure this without special equipment. Factor #3: Atmosphere the product is stored inFoods packed in air don't store as well as in oxygen free gasses. This is because air contains oxygen which oxidizes many of the compounds in food. Food storage companies have a couple of different processes for removing the oxygen:Displacing the oxygen: This is done by purging out all the air in the product with an inert gas. Nitrogen is almost always used because it is the most inert gas known. People doing their own packing occasionally use dry ice which gives off carbon dioxide gas, and probably works just about as well.Absorb the oxygen: Oxygen absorber packets do just that. Air contains about 78% nitrogen and 21% oxygen, leaving about 1% for the other gasses. If the oxygen is absorbed, what remains is 99% pure nitrogen in a partial vacuum.If oxygen absorber packets are used, care must be taken to use a storage container that can stand some vacuum. As air is sucked into your container as the oxygen is absorbed, it reintroduces more oxygen that must be absorbed. Before long, the oxygen absorbers will have absorbed all the oxygen they can. Obviously, your product won't be oxygen free under these circumstances. Walton Feed gets around this problem with their plastic Super Pail buckets by purging the product first with nitrogen before tossing in the two oxygen absorber packets. This way the absorbers have little or no oxygen to absorb and don't create a vacuum within the pail. As cans work well under a partial vacuum, purging them with nitrogen isn't necessary before inserting the oxygen absorber packet and sealing the lid. Large seeds store better in nitrogen. On the other hand, small seeds, like many garden seeds store better in air. For this reason Walton cans their garden seed packs in air. Factor #4: The container the product is stored inTo get the best storage life out of your product it must have a hermetic (air tight) seal. Containers that do this well are:

#10 Cans

Sealable food storage buckets

Sealable food quality metal or plastic drums

Whatever container you use, be sure it is food grade as your product can be tainted with whatever the container is made from. Plastic sacks are not good air tight containers, for even if they are sealed, the relatively thin plastic 'breathes,' allowing air to pass through. Paper sacks are of course even worse.

There is some concern as to how good a seal is made by the lids on plastic buckets used by food storage companies. Manufacturer studies show an extremely small amount of air transfer. This amount is so small, however, that it can be considered a hermetic seal. It has also been found that the lids can be re-used several times without dramatically degrading the performance of the seal. People who purchase products from food storage providers are often concerned about receiving their buckets bulging or with one side collapsed in. Collapsed buckets occasionally occur when ordering from Walton's as the elevation of their packing facility is above 6,000 feet. As the buckets are shipped to a lower elevation, the increased ambient air pressure can sometimes push in one side. If a side is popped in, it is a great indication that the bucket is indeed sealed. And this also holds true for buckets that might be under a slight amount of pressure. If either condition concerns you, crack the lid to equalize the air pressure. You can do this without seriously degrading the storageability of the product within the bucket. Remember to re-seal the lid after doing this. Bulging cans: Some bulging cans have been returned to Waltons. In almost every case, these cans held mixes that contained baking powder or soda. These cans were sent off for bacteria analysis and came back negative. It is believed that occasionally the extremely small amount of moisture found in the product interacts over time with the baking powder or soda and creates a small amount of carbon dioxide gas.

STORAGE LIFE NOTES ABOUT SPECIFIC FOODS

The Soft Grains

Barley

Hulled or Pearled Oat

Groats

Rolled Oats

Quinoa

Rye

Soft Grains have softer outer shells which don't protect the seed interior as well as hard shelled seeds and therefore won't store as long. Hermetically sealed in the absence of oxygen, plan on a storage life of 8 years at a stable temperature of 70oF. They should keep proportionately longer if stored at cooler temperatures.

The Hard Grains

Buckwheat
Corn, Dry
Flax
Kamut

Millet
Durum wheat
Hard red wheat
Hard white wheat

Soft wheat
Special bake wheat
Spelt
Triticale

The Hard Grains all store well because of their hard outer shell which is nature's near perfect container. Remove that container and the contents rapidly deteriorate. Wheat, probably nature's longest storing seed, has been known to be edible after scores of years when stored in a cool dry place. As a general rule for hard grains, hermetically sealed in the absence of oxygen, plan on a storage life of 10-12 years at a stable temperature of 70oF. They should keep proportionately longer if stored at cooler temperatures.Beans

Adzuki Beans
Blackeye Beans
Black Turtle Beans
Garbanzo Beans

Great Northern KidneyBeans
Lentils
Lima Beans
Mung Beans

Pink Beans
Pinto Beans
Small Red Beans
Soy Beans

As beans age they lose their oils, resist water absorption and won't swell. Worst case, they must be ground to be used. Storing beans in nitrogen helps prolong the loss of these oils as does cool temperatures. Hermetically sealed in the absence of oxygen, plan on a storage life of 8-10 years at a stable temperature of 70oF. They should keep proportionately longer if stored at cooler temperatures.Dehydrated Vegetables

Broccoli

Cabbage

Carrots

Celery
Onions

Peppers
Potatoes

Dehydrated vegetables store well if hermetically sealed in the absence of oxygen. Plan on a storage life of 8-10 years at a stable temperature of 70oF. They should keep proportionately longer if stored at cooler temperatures.Dehydrated Dairy Products

Cheese
Powder
Cocoa

Powder
Powder Eggs
Butter/margarine Powder

Powder Milk
Morning Moo Whey Powder

Dehydrated dairy products generally store very well if stored dry in hermetically sealed containers. Plan on a storage life of 15 years if stored at a stable temperature of 70oF. They should keep proportionately longer if stored at cooler temperatures. One exception is Morning Moo. As a new whey based product, it hasn't been tested for long term storage. Plan on rotating this product after 5 years.Flours and Other Products Made From Cracked/Ground Seed

All Purpose Flour
Bakers Flour
Unbleached Flour
White Flour

Whole Wheat Flour
Cornmeal Mixes
Refried Beans

Cracked Wheat
Germade Gluten
Granola Wheat Flakes

After seeds are broken open their outer shells can no longer protect the seed contents and seed nutrients start to degrade. Don't try to store unprotected flours longer than a year. Hermetically sealed in the absence of oxygen, plan on a storage life of 5 years at a stable temperature of 70oF. They should keep proportionately longer if stored at cooler temperatures.Pasta

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